During the paper making process water, refined pulp and other additives are combined to give the finished paper the desired properties. The mix is spread over a mesh screen which forms the paper and lets the water be extracted. The paper then travels through different processes and machines designed to remove the water from the paper. After the paper is dry, the paper is run between drums to give the desired smoothness. This process may be referred to as calendering the paper. The more times paper is calendered the less bulk it has but the smoother the finish of the paper. To create glossy paper, uncoated paper may be coated with a paint-like product and buffed by rollers under very high pressure, to create a shiny appearance. This process may be referred to as supercalendering. Additional varnish layers may be applied to paper during the printing process to provide a gloss surface on the paper. The gloss surface may also protect the paper from the surrounding environment. During the various manufacturing process a continuous roll of paper weaves throughout the machinery of the press. Rolls and presses are used to move the paper between the various manufacturing processes.
To ensure that the paper surface has received the correct amount of gloss, sensors are used to measure the gloss of sample surfaces. Referring to FIG. 1A, sensor 100A may have a light source 102A for providing a light beam 104A to illuminate sample surface 106A at a pass-line. Light beam 104A is reflected off sample surface 106A. The intensity of the reflected light is measured with light detector 108A. The reflected light is measured by light detecting surface 110A of light detector 108A to determine the light intensity of the reflected light. The gloss level is calculated by determining the ratio of the reflecting light beam intensity to the intensity of the illuminating light beam. The intensities of the reflected light are compared with known values of intensity for various gloss sample surfaces.
Referring to FIG. 1B, as the paper moves along the manufacturing process, sample surface 106B of a web of paper may flutter or wave due to vibrations imparted by the devices, applicators, and other machinery used in the manufacturing process. The flutter or wave may cause the sample surface 106B to move to a new sample surface location 112B. The movement of the sample surface 106B may cause errors to the measured gloss values because the optical arrangement of the gloss sensor system may require a very precise geometry in order to operate in a correct manner.
Referring to FIG. 1C, as the paper moves along the manufacturing process, the sample surface 106C of the web of paper may tilt and/or cup due to shifts in the web of paper in both lateral and longitudinal directions. The tilt may cause the sample surface 106C to shift to a new sample surface angle 112C. This may be problematic with on-line measurement applications. The tilt of the sample surface 106C may cause errors to the measured gloss values. The erratic sensor response is caused by the optical arrangement of the gloss measurement. The optics may require a very precise geometry. The light source 102C may reflect the light beam 104C off the sample surface 106C exactly onto the light detecting surface 108C of the light detector 110C.
If sample surface 106B, 106C moves or tilts, some part of the reflected light rays may be lost and the measured signal will be erratic. The current state of the art may provide for precise measurements in a laboratory setting when the sample position can be easily controlled but, as explained above, such control is not easily obtained in a manufacturing environment.
In paper and board manufacturing, non-touching measurement principles may be preferred over sensor techniques that make contact with the paper web. In addition, paper web stabilization techniques such as mechanical sheet stabilizers are also not preferred. For example, the use of mechanical sheet stabilizers can cause scoring on the product surface. Due to such markings, it may be impossible to use sheet stabilizers in certain applications. Also, sheet stabilizers may tend to increase dust and dirt problems by rubbing the moving web. The cross-direction profiles of paper and board webs can have many types of deviations from a straight line. For example, the base cross profile can be warped in many different directions. Because warping or scoring of paper the optimal position of the paper web for on-line gloss measurement is very difficult and sometimes impossible to guarantee.
Accordingly, an efficient and effective device, method, and system is needed for detecting surface characteristics of a sample surface. In addition, the system and method may provide for detecting surface characteristics of a moving sample surface.